This invention relates to a probe for ultrasonic imaging apparatus and, more particularly, to such apparatus used in the diagnosis of a portion of a living human body pierced by a cannula, as in a biopsy.
A biopsy is a necessary examination for diagnosis of various diseases, especially a blood disease. Presently, the biopsy has ordinarily been performed to withdraw tissues or body fluids by a suitable puncturing cannula from the organs of a human body, such as a liver or kidneys, according to the objectives of the diagnosis. Additionally, in a method for imaging a blood vessel utilizing X-ray photography, for example, a blood vessel or the like is pierced by a cannula and a contrast medium is injected into the blood vessel through the cannula by an injector for discovering morbid changes in the cerebrum, heart, abdominal organs or limbs by X-ray photography.
In other examples, amniotic fluid is withdrawn from the uterus through a cannula, or a medication or blood is injected into the fetal body for diagnosis of a pregnant woman.
In the above-mentioned cases, it is necessary that rigid precaution be made that the puncturing cannula does not damage tissue unnecessarily, that tissue is not misguidedly withdrawn from undesired body areas, and that the contrast medium is not misguidedly injected into the wrong portion of the subject.
In the past, the surgeon performing the operation of puncturing the human body with a cannula has, for the most part, had to relay on his own knowledge, experience and intuition. Recently, however, it has become known to utilize ultrasonic imaging to display tomographic images of the subject, as the body is being pierced by the cannula. For effectively using such ultrasonic imaging apparatus, while the cannula is piercing the subject, it is necessary to accurately display the internal objective in the tomographic image by means of the ultrasonic echo image of the puncturing cannula at the time of the piercing. Moreover, it is necessary that sufficient detail be displayed so that the surgeon can make a proper choice of the course of the cannula into the internal diagnosis portion of the objective as displayed. An ultrasonic probe satisfying these two main conditions is already known, as described, for example in U.S. Pat. No. 4,029,084.
In FIG. 1 of this application, there is shown a plurality of ultrasonic transducer elements 3 arranged in a row on the application surface 1 of a support member 2 of such a conventional ultrasonic probe. The elements 3 are individually connected to a cable 4. A guide slot 5 for a puncturing cannula is provided in the support member 2. As shown, the support member 2 is a rectangular block with transducer elements 3 aligned on one face of the block. The guide slot 5 may be formed, for example, through the block and perpendicular to the application face containing the transducer elements. The guide slot 5 preferably tapers from a relatively narrow opening 5a centered among the transducer elements 3 to a relatively wide opening 5b in the face of the block opposite the transducer elements. The surgeon, therefore, inserts the cannula through the slot 5 from the wide opening to the narrow opening, and the cannula can be rotated and shifted obliquely in the tapered slot.
Due to the central position of the cannula among the transducer elements, the cannula can be simultaneously observed by watching the ultrasonic tomographic image of the objective which is obtained with a sequential actuation of the transducer elements 3 at the time the body is pierced by the cannula.
However, sterilization of this conventional ultrasonic diagnosis device presents continuing problems. Although the cannula is completely disinfected before use, it is necessary to sterilize the support member 2 of the ultrasonic probe also because the cannula may be contacted by the guide slot 5 of the support member 2. A gas disinfection method is generally used for sterilization for quick and efficient contact of all surfaces of the support member 2. It has been found that the binding force of the binding agent used to secure the transducer elements 3, and other members not shown, to the support member is weakened, causing their peeling off, because the gas permeates through very small spaces between the joining portions of the support member 2 or between the support member 2 and the plurality of transducer elements. Since the ultrasonic probe must be sterilized repeatedly, not only is the useful life of the probe shortened, but there is the continuing danger that the probe may be rendered useless at very inconvenient times.
Furthermore, the probe often needs to be used on several subjects in quick succession and the sterilization of the probe is inconvenient and time-consuming. Perhaps most importantly, due to its construction, it is not possible to be sure that the probe has been completely disinfected by the gas treatment.